Electric compressed-gas circuit breaker

ABSTRACT

An electric compressed-gas circuit breaker is disclosed and has two stationary contact pieces. A switching unit is movable between closed and open positions for electrically bridging the contact pieces in the closed position and for electrically disconnecting the contact pieces in the open position whereby an arc develops when the switching unit is moved to the open position. A gas-blast arrangement blasts a stream of gas through the arc when the switching unit is moved to the open position. The switching unit includes a supporting body and a slide-contact ring made of arc-resistant material slideably contacting one of the contact pieces in the closed position. The ring is mounted on the supporting body so as to be electrically insulated therefrom. A plurality of elongated contact elements are disposed in the supporting body for electrically connecting the contact pieces when the switching unit is in the closed position. The contact elements are spring loaded to displace the same into electrically conductive contact with the slide-contact ring as the ring and the contact elements separate from the one contact piece when the switching unit moves into the open position.

United States Patent [191 Beier et al.

{ 1 ELECTRIC COMPRESSED-GAS CIRCUIT BREAKER [75] Inventors: Helmut Beier; Siegfried Handke; Wolfgang Konczal, all of Berlin, Germany [73] Assignee: Siemens Aktiengesellschaft, Munich,

Germany 22 Filed: Feb. 22, 1973 21 Appl.No.:334,934

[30] Foreign Application Priority Data Feb. 22, 1972 Germany 2209287 [52] US. Cl 200/148 R [51] Int. Cl. H0111 33/82 [58] Field of Search 200/148 R [56] References Cited FOREIGN PATENTS OR APPLICATIONS 1,965,853 6/1971 Germany 200/148 R Primary Examiner-Robert S. Macon Attorney, Agent, or FirmKenyon & Kenyon Reilly Carr & Chapin [451 Jan. 29, 1974 ABSTRACT An electric compressed-gas circuit breaker is disclosed and has two stationary contact pieces. A switching unit is movable between closed and open positions for electrically bridging the contact pieces in the closed position and for electrically disconnecting the contact pieces in the open position whereby an arc develops when the switching unit is moved to the open position. A gas-blast arrangement blasts a stream of gas through the are when the switching unit is moved to the open position. The switching unit includes a supporting body and a slide-contact ring made of arcresistant material slideably contacting one of the contact pieces in the closed position. The ring is mounted on the supporting body so as to be electrically insulated therefrom. A plurality of elongated contact elements are disposed in the supporting body for electrically connecting the contact pieces when the switching unit is in the closed position. The contact elements are spring loaded to displace the same into electrically conductive contact with the slide'contact ring as the ring and the contact elements separate from the one contact piece when the switching unit moves into the open position.

7 Claims, 9 Drawing Figures PAINTED- SHEET 1 BF 4 Fig. 1

ELECTRIC COMPRESSEUGAS CIRCUIT 1 BREAKER BACKGROUND OF THE INVENTION Deutsche Offenlegungsschrift No. 1,913,973 discloses an electric circuit breaker with a blasting arrangement consisting of a piston and a cylinder and includes two stationary, nozzle-shaped contacts and a bridging contact member which connects the stationary contacts in the closed position. The bridging contact member carries a sliding contact ring of arcresistant material and includes spring-loaded contact members which in the closed position are pressed with the predetermined contact pressure against the corresponding stationary contact under the force of springs corresponding to these members. The cylinder of the blasting arrangement is rigidly coupled with the bridging contact member, so that in the open position it is moved in the same direction as the bridging contact member in the course of the switching motion. The cylinder coacts with the relatively stationary piston of the blasting arrangement so that during the breaking motion the gaseous quenching medium, particularly sulfur hexafluoride (SP is driven into the region of the gap between the two stationary, nozzle-shaped contacts. The known electric circuit breaker operates as a socalled single-pressure circuit breaker.

German Pat. No. 1,212,617 discloses a contact arrangement for compressed-gas circuit breakers (dualpressure circuit breakers) wherein the powerinterrupting gap consists of two coaxial nozzle tubes which are arranged at a fixed distance from each other and which are provided with slots for the purpose of generating a magnetic blasting field. With the nozzle tubes are associated a common blast valve and a movable bridging contact member which is configured as a tulip-shaped contact and bridges the two nozzle tubes in the closed position. The bridging contact member comprises contact fingers as well as a ring electrode built ahead of these contact fingers with radial slots, the inside diameter of which is larger than the outside diameter of the nozzle tubes. During the opening motion an arc is drawn between the one stationary nozzle tube and the contact fingers, which is to jump, that is commutate, to the ring electrode in the further course of the switching motion. Under the-action of the magnetic blasting field, the are which is burning between the ring electrode and the one nozzle tube, is then driven toward the axis of the nozzle tube, so that in the course of the further switching motion the arc commutates a second time, whereby its starting point gets to the opposite stationary nozzle tube. This arrangement has the disadvantage that the arc must jump gaps supplied with insulating quenching gas twice and that the contact fingers are subjected, at least briefly, to the high temperaures of the arc base, which results in a reduction of the contact life.

SUMMARY OF THE INVENTION The invention relates to an electric compressed-gas circuit breaker of the so-called single-pressure type. The circuit breaker includes a blasting arrangement consisting of a piston and a cylinder, two stationary nozzle-shaped contacts and a bridging contact unit connecting them in the closed position. The bridge member is equipped with a slide-contact ring of arcresistant material and spring-loaded contact elements.

It is an object of the invention to provide a compressed-gas circuit breaker wherein the arc commutates only once during the switching motion. Subsidiary to this object, it is an object of the invention to force the current feeding the are into an unequivocally predetermined path through the bridging contact member.

The electric compressed-gas circuit breaker of the invention includes as a feature two stationary contact pieces and a bridging member in the form of a switching unit which is movable between closed and open positions for electrically bridging the contact pieces in the closed position and for electrically disconnecting the contact pieces in the open position whereby an are develops when the switching unit is moved to the open position. Gas-blast means are provided for blasting a stream of gas through the arc when the switching unit is moved to the open position. The switching unit includes a supporting body and a slide-contact ring made of arc-resistant material slideably contacting one of the contact pieces in the closed position. The ring is mounted on the supporting body so as to be electrically insulated therefrom. A plurality of elongated contact elements are disposed in the supporting body for electrically connecting the contact pieces when the switching units is in the closed position. Spring means spring load the contact elements to displace the same into electrically conductive contact with the slide-contact ring as the ring and the contact elements separate from the one contact piece when the switching unit moves into the open position.

This configuration assures that the contact elements, when lifted from the stationary contact, come into engagement with the slide-contact ring which is carried by the switching unit in an insulated manner, so that no arc can occur between the stationary contact and the contact elements. This in itself could also be achieved by a metallic connection between the slide-contact ring and the switching unit; this, however, could lead in the arc, which burns between the slide-contact ring and the one stationary nozzle-shaped contact, to a branching of the current into parallel paths with a dynamic effect on the Contact system which is unfavorable in the case of large currents, that is, the contact elements could get lifted on the side of the slide-contact ring. For this reason and according to a feature of the invention, the switching unit carries the slide-contact ring with electrical insulation interposed.

The gas-blast means includes a cylinder for holding the gas therein, and a piston mounted in the cylinder. The cylinder and the piston are mounted with respect to the switching unit so as to cause a relative movement between the piston and the cylinder when the switching unit moves to the open position to impart sufficient energy to the gas for blasting the same through the arc. The contact pieces have a nozzle-like configuration for receiving the gas blasted through the are.

In a preferred embodiment of the electric compressed-gas circuit breaker according to the invention, the slide-contact ring has on its end face which faces the contact elements a protruding rim which forms a cage for the spring-loaded contact elements. As the contact elements separate from stationary contact, the contact elements are acted upon by springs associated therewith and are therefore braced against the protruding rim of the sliding contact ring and establish a good, electrically conducting connection.

In a further embodiment, the electrical insulation on the free end face of the switching unit forms a slider member which cooperates. with the one stationary contact in the region of the closed position. This slider, which can surround the contact with a small amount of play, exposes the gap between the stationary contacts for the quenching gas compressed by the blasting arrangement only after a certain advance of the contact system toward the already drawn arc, so that the compressed quenching and insulating gas is saved up until the arc has reached a length sufficient for favorable control. The arrangement of the slider member results in the additional advantage that small inductive currents can also be reliably interrupted. When such inductive currents are interupted,'the danger exists with a heavy blasting of the arc, that the are which is only poorly developed because of the small current, is broken off prior to the zero crossing of the current; this leads to excessive overvoltages. Through the slider member the blast via a ring gap in the short initial region of the switching movement, in which arcs of small inductive currents could be interrupted prematurely, is choked off, so that the undesired interruption of the arc is prevented. v

A particular advantage results if the slider member is provided with a conical nozzle opening for directing the stream of quenching gas. In this manner the flow of quenching gas, which is generated by the blasting arrangement, is driven not only in the radial direction in the region of the arc; a substantial axial gas flow component, which drives the are into the center of the nozzle-shaped contacts, is also obtained.

The advantage obtained by the projecting slider member and the conical nozzle opening thereof consists in the fact that because the front edge of the sliding contact ring is covered up, the arc is caused to form a loop. Thus, the tendency of the arc to leave the plane of its base at right angles is utilized. The electrodynamic forces generated by the loop formation have the same direction as the forces which the gas stream exerts on the arc. The forces drive the arc toward the center of the contacts.

From the German Pat. No. 1,212,617 a-cylindrical extension of insulating material is known which is supported by the ring electrode of the briding contact member and whose inside diameter corresponds to that of the ring electrode which has, as already mentioned above, an inside diameter which is larger than the outside diameter of the nozzle tubes. From this it followsthat the known cylindrical extension is not a slider member in the sense of the invention, as the compressed quenching and insulating gas can continuously flow just as freely through the gap formed by the cylindrical extension of insulating material and the outer cylinder surface of the stationary nozzle tube as it can through the slots in the ring electrode. A delayed release of the gas flow as in the invention, which makes an advance of the contact system available, is not possible in the known contact arrangement according to the German Pat. No. 1,212,617.

The generation of an axial gas stream component favorable for the quenching of the arc by the conical nozzle opening of the slider member can be improved if the stationary nozzle-shaped contacts are made asymmetrical, as disclosed in Deutsche Auslegungsschridt No. 1,190,077, wherein the contact facing the sliding contact ring has a smaller nozzle orifice than the opposite stationary contact.

Although the invention is illustrated and described herein as an electric compressed-gas circuit breaker, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein within the scope and the range of the claims. The invention, however, together with additional objects and advantages will be best understood from the following description and in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram, in longitudinal section, of an electric compressed-gas circuit breaker according to the invention. The left-half of the diagram shows the switching unit in the open position and the right half, the closed position.

FIGS. 2 to 7 show the contact arrangement of the electric compressed-gas circuit breaker according to FIG. 1 for different positions of the switching unit during the opening movement.

FIG. 8 illustrates another embodiment of the circuit breaker according to FIG. 1 wherein the switching unit is equipped with a slider member for delaying the exposure of the contact gap to the blasting gas.

FIG. 9 illustrates a modification of the embodiment of FIG. 8 wherein the slider member is provided with conical nozzle aperture.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The high-voltage circuit breaker of FIG. 1 can be operated, for example, at 1 10 kV and canuse sulfur hexafluoride as the quenching and insulating medium. In order to more clearly depict the portions of the breaker pertinent to the invention, only those parts which are necessary for understanding the invention are shown. The parts of the circuit breaker which are at ground potential, the actuator and the standoff insulators are not illustrated. The electric circuit breaker is constructed as a compressed-gas breaker and has a switching chamber l which consists, for example, of porcelain and supports at its upper end a connecting member, not shown in detail. A hollow metallic body 2 is attached to this connecting member. The body 2 protrudes into the interior of the switching chamber 1 and carries a stationary contact 3. Opposite the contact 3 is a stationary contact 4. Both contacts 3 and 4 are made hollow to carry away the switching gases and are configured as nozzles at their respective end faces disposed opposite each other. Y V

In the closed position, the two stationary contacts 3 and 4 are connected by a switching unit in the form of a bridging contact member 6 having a tubular configuration. Spring-loaded elongated elements 7 are disposed inside contact member 6 and have contact areas 8 which are pushed against the stationary contacts 3 and 4 with a predetermined contact pressure. The bridging contact member 6 carries a slide-contact ring 9 of arc-resistant, electrically conductive material with electrical insulation 10 interposed. The tubular bridg ing contact member 6 is screwed into a coupling member 18 which in turn is connected via fastening elements 19 with a tube 20 of insulating material. The tube 20 constitutes a blast cylinder.

On its face 21, the blast cylinder carries a nozzleshaped body which surrounds the stationary contact 3. The insulating tube 20, for example, is made of one piece of material such as fiber-reinforced plastic. During the opening motion, the insulating tube 20 is pulled, together with the bridging contact member 6, over a relatively stationary piston 24, so that a quenching me dium flow is prepared. Tie rods 12 engage the coupling member 18 and are pivotally supported at a pin 13. A drive member (not shown in detail) is coupled to the tie rods 12 and moves the breaker from the closed position shown to the right of the center line to the open position shown to the left.

The switching chamber 1 is completely filled with sulfur hexafluoride at a pressure of, for example, 4 kg/cm When the breaker opens, the contact member 6, together with the tube 20, moves from the top to the bottom. The sulfur hexafluoride inside the tube 20 is compressed in this process because it cannot yet flow out at the beginning of the opening motion. Only when the tube 20 has travelled about half of its stroke do the contact elements 7 of the bridging contact member 6 and the contact ring 9 slide off the stationary contact 3, so that with the metallic separation a discharge clearance is created. The sulfur. hexafluoride, compressed up to this point, flows through the discharge clearance to the discharge nozzles which are formed by the two stationary contacts 3 and 4. The arc is commutated here from the contact ring 9 to the burn-off electrodes made of arc-resistant material provided at the contact 4 and is quenched because of the favorable flow conditions which prevail at the nozzles.

In the open position the gap between the contacts 3 and 4 is free. The field strength there is low because the contacts, being electrodes of large area, produce a uniform field.

FIG. 2 is a section view of the stationary contacts 3 and 4 and the bridging contact member 6. Here, the bridging contact member 6 is still engaged and the contact elements 7 are braced with their contact surfaces 8 under the pressure of their springs 17 against the cylindrical outside surface of the stationary contact 3. The current flows along a path indicated by the broken line. In the course of the opening motion, the bridging contact member 6 moves into the position shown in FIG. 3, where the contact elements 7 are not yet separated from the contact 3, but rest with projecting extensions 16 on a protruding rim of the sliding contact ring 9. The sliding contact ring 9 forms with its protruding rim 15 a cage for the contact elements 7. In the position of the contacts shown in FIG. 3, the current flows from the contact 3 via the sliding contact ring to the contact elements 7 and from there to the contact 4.

As shown in FIG. 4, in the further course of the opening motion, the current flows only via the sliding contact ring 9 which is supported by the bridging contact member 6 via the electrical insulation 10. This results in a well-defined current path which cannot lead to undesirable dynamic action on the contact system.

In the position of the bridging contact member 6 seen in FIG. 5, an are 30 is drawn at the contact 3 after the sliding contact ring 9 is separated, the one foot point of which is at the contact 3 and the other foot point at the sliding contact ring 9. The arrangement of the sliding contact ring 9 and the electrical insulation 10 which supports this ring is additionally configured so that the are 30 cannot shift its foot point from the sliding contact ring 9 as, for example, to the outer tube of the bridging contact member 6. The insulation 10 therefore forms a barrier for the arc to prevent the arc from wandering away.

FIG. 6 shows a position of the bridging contact member 6 whereat the are 30 commutates from the sliding contact ring 9 to the contact 4. In the contact arrangement shown in FIG. 7, the arc bums between the two stationary contacts 3 and 4.

FIG. 8 shows how the insulation 10 can be provided with a slider member 31 which is situated in front of the slide-contact ring 9 and forms the free end of the bridging contact member 6. The slider member 31 surrounds the bridging contact member 6 in the position shown with a small gap so that in the case of small arcs, which occur when small inductive currents are interrupted, no gas flow or only a slight gas flow results initially after the sliding contact ring 9 is separated from the contact 3. The slider member 31 then chokes off the gas flow. Only when slider member 31 releases the gas flow does the gas begin to blast the are so that the danger of a break off prior to the zero crossing of the current, and thereby, the danger of o'vervoltages is largely eliminated.

It is advantageous to provide the slider member 31 with a conical nozzle aperture 32 as shown in FIG. 9 which serves to direct the stream of quenching gas. The conical nozzle aperture causes, in addition to the radial flow component, a gas flow in the axial direction, which drives the arc 30 toward the center of the contacts 3,4. This effect of the conical nozzle opening can be aided, as shown in FIGS. 2 to 9, by an asymmetrical nozzle arrangement of the two contacts 3 and 4. in which the nozzle of the contact 4 has a larger diameter than that of the contact 3.

The slider member 31 provides the further advantage that the blasting arrangement is better protected against the thermal arc radiation. Instead of the polytetrafluoroethylene used for high-power circuit breakers, in some applications cast resin can be used which has been used successfully so far in other circuit breakers. The slider member 31 covers up the end face of the sliding contact member 9, so that the arc is forced to form a loop to the stationary contact 3. The electrodynamic forces produced here drive the arc in the desired manner together with the gas stream 33 into the center of the contacts 3 and 4.

What is claimed is:

1. An electric compressed-gas circuit breaker comprising two stationary contact pieces; a switching unit movable between closed and open positions for electrically bridging said contact pieces in the closed position and for electrically disconnecting said contact pieces in the open position whereby an arc develops when said switching unit is moved to the open position; and gasblast means for blasting a stream of gas through the arc when said switching unit is moved to the open position; said switching unit including a supporting body, a slidecontact ring made of arc-resistant material 'slideably contacting one of said contact pieces in the closed position, said ring being mounted on said supporting body so as to be electrically insulated therefrom, a plurality of elongated contact elements disposed insaid supporting body for electrically connecting said contact pieces when said switching unit is in the closed position, and

spring means for spring loading said contact elements to displace the same into electrically conductive contact with said slide-contact ring as said ring and said contact elements separate from said one contact piece when said switching unit moves into the open position.

2. The circuit breaker of claim 1, said gas-blast means comprising a cylinder for holding the gas therein, and a piston mounted in said cylinder, said cylinder and said piston being mounted with respect to said switching unit so as to cause a relative movement between said piston and said cylinder when said switching unit moves to the open position to impart sufficient energy to the gas for blasting the same through the arc, said contact pieces having a nozzle-like configuration for receiving the gas blasted through the arc. 3. The circuit breaker of claim 2 comprising a layer of insulation material disposed between said supporting body and said slide-contact ring, said slide-contact ring having an end face directed toward said contact elements, said ring having a rim projecting from said end face to an extent sufficient to form a cage for said contact elements.

4. The circuit breaker of claim 2, said contact pieces having respective contours asymmetrical with respect to each other, said one contact piece having a smaller nozzle opening than the other one of said two contact pieces.

5. The circuit breaker of claim 2 comprising a layer of insulation material disposed between said supporting body and said slide-contact ring, said layer having an end portion directed away from said slide-contact ring, said end portion being configured as a slider body for coacting with said one stationary contact piece to choke the gas from said gas-blast means in the initial movement of said switching unit to the open position.

6. The circuit breaker of claim 2, said slider body having a conical nozzle opening for directing the flow of the gas to the arc.

7. The circuit breaker of claim 6, said contact pieces having respective contours asymmetrical with respect to each other, said one contact piece having a smaller nozzle opening than the other one of said two contact pieces. 

1. An electric compressed-gas circuit breaker comprising two stationary contact pieces; a switching unit movable between closed and open positions for electrically bridging said contact pieces in the closed position and for electrically disconnecting said contact pieces in the open position whereby an arc develops when said switching unit is moved to the open position; and gasblast means for blasting a stream of gas through the arc when said switching unit is moved to the open position; said switching unit including a supporting body, a slide-contact ring made of arc-resistant material slideably contacting one of said contact pieces in the closed position, said ring being mounted on said supporting body so as to be electrically insulated therefrom, a plurality of elongated contact elements disposed in said supporting body for electrically connecting said contact pieces when said switching unit is in the closed position, and spring means for spring loading said contact elements to displace the same into electrically conductive contact with said slide-contact ring as said ring and said contact elements separate from said one contact piece when said switching unit moves into the open position.
 2. The circuit breaker of claim 1, said gas-blast means comprising a cylinder for holding the gas therein, and a piston mounted in said cylinder, said cylinder and said piston being mounted with respect to said switching unit so as to cause a relative movement between said piston and said cylinder when said switching unit moves to the open position to impart sufficient energy to the gas for blasting the same through the arc, said contact pieces having a nozzle-like configuration for receiving the gas blasted through the arc.
 3. The circuit breaker of claim 2 comprising a layer of insulation material disposed between said supporting body and said slide-contact ring, said slide-contact ring having an end face directed toward said contact elements, said ring having a rim projecting from said end face to an extent sufficient to form a cage for said contact elements.
 4. The circuit breaker of claim 2, said contact pieces having respective contours asymmetrical with respect to each other, said one contact piece having a smaller nozzle opening than the other one of said two contact pieces.
 5. The circuit breaker of claim 2 comprising a layer of insulation material disposed between said supporting body and said slide-contact ring, said layer having an end portion directed away from said slide-contact ring, said end portion being configured as a slider body for coacting with said one stationary contact piece to choke the gas from said gas-blast means in the initial movement of said switching unit to the open position.
 6. The circuit breaker of claim 2, said slider body having a conical nozzle opening for directing the flow of the gas to the arc.
 7. The circuit breaker of claim 6, said contact pieces having respective contours asymmetrical with respect to each other, said one contact piece having a smaller nozzle opening than the other one of said two contact pieces. 